Method and apparatus for minimizing redundant enhanced uplink allocation requests and fault-isolating enhanced uplink transmission failures

ABSTRACT

A method and apparatus for minimizing redundant enhanced uplink (EU) allocation requests and fault-isolating EU transmission failures that occur between a wireless transmit/receive unit (WTRU) and a Node-B. The WTRU transmits an enhanced dedicated channel (E-DCH) allocation request to the Node-B over an uplink (UL) EU channel. In one embodiment, if E-DCH allocation cannot be provided within a predetermined time period, the Node-B sends an acknowledgement message to the WTRU via a downlink (DL) EU signaling channel without sending E-DCH allocation information. The request is queued in the Node-B and the WTRU refrains from transmitting the same request until after the time period expires or resources become available. In another embodiment, appropriate actions are taken to correct EU transmission failures by determining whether an E-DCH allocation request was unsuccessfully delivered via the UL EU channel or whether channel allocation information was unsuccessfully delivered via the DL EU signaling channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/114,390 filed Apr. 26, 2005, which claims the benefit of U.S.Provisional Application No. 60/567,144 filed Apr. 30, 2004, which areincorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to a wireless communication systemincluding a wireless transmit/receive unit (WTRU), at least one Node-Band a radio network controller (RNC). More particularly, the presentinvention is a method and apparatus for minimizing redundant enhanceduplink (EU) allocation requests and fault-isolating EU transmissionfailures.

BACKGROUND

Methods for improving uplink (UL) coverage, throughput and transmissionlatency are being investigated in Release 6 (R6) of the 3rd GenerationPartnership Project (3GPP). In order to successfully implement thesemethods, the scheduling and assigning of UL radio resources have beenmoved from a radio network controller (RNC) to a Node-B such that theNode-B can make decisions and manage UL radio resources on a short-termbasis more efficiently than the RNC, even if the RNC retains overallcontrol over the Node-B.

In order for the WTRU to transmit on enhanced dedicated channel (E-DCH),the WTRU must identify the need for E-DCH transmissions by transmittingE-DCH channel allocation requests to the Node-B. Then, the Node-Bprovides allocation of E-DCH physical resources to the WTRU that haverequested the E-DCH channel.

When there are not enough UL resources for the E-DCH channel allocationrequests, the Node-B cannot immediately allocate resources of E-DCHtransmission for all WTRUs that have requested the E-DCH. If the WTRUdoes not receive an E-DCH allocation within a predetermined time period,the WTRU may retransmit the request until the WTRU receives E-DCHchannel allocation information.

Since the transmission of an E-DCH channel allocation request interfereswith other WTRUs, when each WTRU transmits and retransmits the samechannel allocation request multiple times, the UL EU channel willincrease UL interference. Thus, the overall efficiency of the systemwill be degraded.

Therefore, there is a need to minimize utilization of the UL signalingchannel while maintaining proper EU scheduling operation. Furthermore, aprocedure for fault-isolating EU transmission failures is desired.

SUMMARY

The present invention is a method and apparatus for minimizing redundantEU allocation requests and fault-isolating EU transmission failures thatoccur between a WTRU and a Node-B. The WTRU transmits an enhanceddedicated channel (E-DCH) allocation request to the Node-B over a UL EUchannel when the WTRU has scheduled E-DCH data to transmit.

In one embodiment, the Node-B receives the channel allocation requestand determines whether channel allocation can be provided for the WTRUwithin a predetermined channel request response time period. If channelallocation for the WTRU can be provided within the predetermined channelrequest response time period, the Node-B sends scheduling information,(i.e., E-DCH channel allocation information), to the WTRU. Otherwise,the Node-B only sends an acknowledgment message to the WTRU indicatingthat the channel allocation request has been received without sending achannel allocation. In response to the acknowledgement message, the WTRUrefrains from transmitting the same channel allocation request for apredetermined maximum time to allocate period and the request is queuedin the Node-B. If the maximum time to allocate period expires withoutreceiving a channel allocation, the WTRU retransmits the channelallocation request.

In another embodiment, appropriate actions are taken to correct EUtransmission failures by determining whether an E-DCH allocation requestwas unsuccessfully delivered via the UL EU channel or whether channelallocation information was unsuccessfully delivered via the DL EUsignaling channel.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1 is a block diagram of a wireless communication system inaccordance with the present invention;

FIG. 2 is a flow diagram of a process for reducing congestion in a UL EUchannel established in the system of FIG. 1 in accordance with oneembodiment of the present invention; and

FIG. 3 is a flow diagram of a process for determining signaling channelfailure during channel allocation and taking corrective actions inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “Node-B”includes but is not limited to a base station, a site controller, anaccess point or any other type of interfacing device in a wirelessenvironment.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 1 is a block diagram of a wireless communication system 100 inaccordance with the present invention. The system 100 includes a WTRU102, one or more Node-Bs 104 and an RNC 106. The RNC 106 controlsoverall EU operation by configuring EU parameters for the Node-B 104 andthe WTRU 102, such as maximum allowed EU transmit power or availablechannel resources per Node-B. The WTRU 102 sends a channel allocationrequest to the Node-B 104 via a UL EU channel 110 and the Node-B 104sends channel allocation information via one or more downlink (DL) EUsignaling channels 112. After EU radio resources are allocated for theWTRU 102, the WTRU 102 transmits data via the UL EU channel 110. TheNode-B 104 includes a request priority queue 114 for queuing E-DCHallocation requests and a maximum time to allocate timer 116 forestablishing an E-DCH allocation request response time period. The WTRUincludes a channel allocation response timer 118 for generating periodicchannel allocation requests when a channel allocation has not beenreceived from the Node-B 104.

FIG. 2 is a flow diagram of a process 200 for reducing congestion in theUL EU channel 110 in accordance with one embodiment of the presentinvention. When the WTRU 102 has E-DCH data to transmit, the WTRU 102sends an E-DCH allocation request to the Node-B 104 via the UL EUchannel 110 (step 202). The signaling of the E-DCH allocation requestmay be either physical or medium access control (MAC) layer signaling.

Upon receiving the E-DCH allocation request from the WTRU 102, theNode-B 104 determines whether there are resources available forallocation of the E-DCH to the WTRU within a predetermined channelrequest response time period (step 204). The channel request responsetime period is a maximum time period within which the Node-B 104 shouldrespond to the channel allocation request. The channel request responsetime period established by the maximum time to allocate timer 116 of theNode-B 104 is activated when the E-DCH allocation request is received bythe Node-B 104. The channel request response time period may be a fixedvalue in the system or configured by the RNC 106 for each EU radioaccess bearer (RAB) and signaled to both the Node-B 104 and the WTRU102.

If E-DCH resources are available, the Node-B 104 sends anacknowledgement message to the WTRU 102 indicating that the E-DCHallocation request has been received (step 206), and also sendsscheduling information, (i.e., E-DCH allocation information), within thechannel request response time period via the DL EU signaling channel 112(step 207). The WTRU 102 then transmits data through the UL EU channel110 in accordance with the scheduling information (step 208).

If the E-DCH resources cannot be allocated before the channel requestresponse time period expires, the Node-B 104 sends an acknowledgementmessage to the WTRU 102 indicating that the E-DCH allocation request hasbeen received, but does not send scheduling information to the WTRU 102before the channel request response time period expires (step 210). Theacknowledgement message does not include scheduling information, butmerely confirms that the Node-B 104 has received the channel allocationrequest and will process the request when resources become available.

In accordance with one embodiment of the present invention, the E-DCHallocation request indicates a priority. After sending theacknowledgement message to the WTRU 102 confirming reception of theE-DCH allocation request, the E-DCH allocation request is stored in arequest priority queue 114 in the Node-B 104 based on the indicatedpriority of the request (step 212). When the request is placed in therequest priority queue 114, the maximum time to allocate timer 116 isactivated or, equivalently, the time of reception of the E-DCHallocation request is recorded. The maximum time to allocate is amaximum time period within which the E-DCH allocation request should beserved before the E-DCH allocation request is finally determined to havefailed. The maximum time to allocate may be unique to each transmissionthat maps to a particular data flow or data priority class.

The requests within the request priority queue 114 in the Node-B 104 maybe serviced on a first-in first-out (FIFO) basis. If there are notenough resources, the allocation is further delayed until it becomesavailable. If there are available resources, the Node-B 104 services atleast one request in the request priority queue 114.

Upon receiving the acknowledgement message from the Node-B 104 inresponse to receiving the E-DCH allocation request, the WTRU 102 checkswhether scheduling information was also received, or whether only thereception of the channel allocation request was acknowledged. If thescheduling information was received, the WTRU 102 transmits data throughthe UL EU channel 110 according to the scheduling information specifiedby the Node-B 104 (step 208). If only an acknowledgement of reception ofthe E-DCH allocation request was received, the WTRU 102 knows that theNode-B 104 has received the E-DCH allocation request and refrains fromretransmitting the same request (step 214).

After the channel allocation request has been received and confirmedwithout scheduling information, the Node-B 104 may provide EU channelallocations later on for the WTRU 102 whose requests have been queued inthe request priority queue 114 of the Node-B 104. Periodically,potentially each transmit time interval (TTI) at step 216, the Node-B104 determines whether resources are available for allocation for therequests in the request priority queue 114 (step 218). If there areresources available, the process 200 proceeds to steps 207 and 208.

If there are no resources available, the Node-B 104 determines whetherthe maximum time to allocate timer 116 expired (step 220).

If the maximum time to allocate timer 116 did not expire, as determinedat step 220, the process 200 waits for the next TTI at step 216. TheNode-B 104 may prioritize allocations that are close to expiration ofthe maximum time to allocate.

After the maximum time to allocate timer 116 has expired or,equivalently, a predetermined time period elapses after the recordedrequest reception time, the WTRU 102 relies on its channel allocationresponse timer 118 for tracking the maximum allocate time period foreach E-DCH allocation request. The WTRU 102 sets the channel allocationresponse timer 118 each time the WTRU 102 sends an E-DCH allocationrequest to the Node-B 104, and recognizes the allocation failure uponexpiration of the channel allocation response timer 118. Alternatively,if the WTRU 102 does not maintain its own equivalent channel allocationresponse timer 118, the Node-B 104 notifies the WTRU 102 of the failureof allocation. If the WTRU 102 maintains its own channel allocationresponse timer 118, there is no need for the Node-B 104 to notify theWTRU 102 of the failure.

When the E-DCH allocation failure occurs, the WTRU 102 has severaloptions. The WTRU 102 may retransmit the E-DCH allocation request or anupdated request to the Node-B 104 (step 224). Step 224 may be performedon a periodic basis, each time the channel allocation response timer 118expires. Alternatively, the WTRU 102 may discard the data for which itrequested an allocation and send an updated E-DCH allocation request ifthe WTRU 102 has more E-DCH data to transmit (step 226).

FIG. 3 is a flow diagram of a process 300 for determining signalingchannel failure during channel allocation in accordance with anotherembodiment of the present invention. When the WTRU 102 has EU data to betransmitted, the WTRU 102 sends an E-DCH allocation request to theNode-B 104 and activates the channel allocation response timer 118 (step302). After sending the E-DCH allocation request, the WTRU 102 waits toreceive scheduling information, (i.e., E-DCH allocation information),from the Node-B 104 until the channel allocation response timer 118expires. If the WTRU 102 fails to receive scheduling information fromthe Node-B 104 before the channel allocation response timer 118 expires(step 304), the WTRU 102 retransmits the same E-DCH allocation requestwith a retransmission indicator or an updated E-DCH allocation request(step 306).

In this case, the WTRU 102 does not know if either the UL EU signaling,(i.e., E-DCH allocation request), or the DL EU signaling, (i.e., channelallocation), is lost. If the Node-B 104 receives a retransmitted E-DCHallocation request (step 308), the Node-B 104 determines where thefailure occurs, (i.e., either the E-DCH allocation request in the UL EUchannel 110 or the channel allocation through the DL EU signalingchannel 112). If the Node-B 104 receives a retransmitted E-DCHallocation request which was not served, the Node-B 104 determines thatthe E-DCH allocation request was not delivered successfully on the UL EUchannel 110 (step 312). If the Node-B 104 receives a retransmitted E-DCHallocation request which was served, the Node-B 104 determines that thechannel allocation information was not delivered successfully on the DLEU signaling channel 112 (step 314). For either of steps 312 and 314,the Node-B 104 then takes appropriate corrective actions in accordancewith the determined failure. The Node-B 104 then processes the receivedrequest (step 316).

The present invention assures that E-DCH allocation requests have beenreceived by the Node-B 104 and the EU UL signaling load is minimizedwhen the E-DCH channel allocation is not immediately provided by theNode-B 104. Using the method of the present invention results in a moreefficient use of UL physical resources.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

While the present invention has been described in terms of the preferredembodiment, other variations which are within the scope of the inventionas outlined in the claims below will be apparent to those skilled in theart.

What is claimed is:
 1. A method for minimizing enhanced dedicatedchannel (E-DCH) allocation requests by a wireless transmit/receive unit(WTRU), the method comprising: the WTRU requesting an E-DCH allocationwith or without transmission data; and on a condition that E-DCHallocation information is not received within a first predeterminedchannel request response period after E-DCH allocation is requested bythe WTRU, the WTRU re-requesting the E-DCH allocation or requesting anupdated E-DCH allocation, wherein the WTRU refrains from furtherrequesting the E-DCH allocation for a second predetermined channelrequest response period.
 2. A method for minimizing enhanced dedicatedchannel (E-DCH) allocation requests by a wireless transmit/receive unit(WTRU), the method comprising: requesting an E-DCH allocation fortransmission of first data, receiving an acknowledgement message of theallocation request without receiving allocation information, refrainingfrom further requesting the E-DCH allocation for a predetermined channelrequest response period in response to the acknowledgment message; andon a condition that the predetermined channel request response periodhas expired and the WTRU has second data to transmit, the WTRU requestsan E-DCH allocation for transmission of the first data and the seconddata.
 3. The method of claim 2, wherein the E-DCH allocation isrequested including transmission data.
 4. A method for minimizingenhanced dedicated channel (E-DCH) allocation requests by a wirelesstransmit/receive unit (WTRU), the method comprising: requesting an E-DCHallocation, determining whether an acknowledgement message of theallocation request is received; and on a condition that anacknowledgment message of the allocation request is not received,re-requesting the E-DCH allocation or requesting an updated E-DCHallocation and refraining from further requesting the E-DCH allocationfor a predetermined channel request response period.
 5. The method ofclaim 4, wherein the E-DCH allocation is re-requested or the requestingthe updated E-DCH allocation is requested after expiration of thepredetermined channel request response period.
 6. The method of claim 5,wherein the E-DCH allocation is re-requested or the updated E-DCHallocation is requested with a retransmission indicator.
 7. The methodof claim 4, wherein the E-DCH allocation is re-requested or the updatedE-DCH allocation is requested prior to expiration of the predeterminedchannel request response period.
 8. The method of claim 7, wherein theE-DCH allocation is re-requested or the updated E-DCH allocation isrequested with a retransmission indicator.
 9. A method for minimizingenhanced dedicated channel (E-DCH) allocation requests by a wirelesstransmit/receive unit (WTRU), the method comprising: requesting an E-DCHallocation, prioritizing the E-DCH allocation request; and receiving anacknowledgment message of the E-DCH allocation request, withoutreceiving allocation information, wherein the priority of the E-DCHallocation request is a factor determining whether the WTRU will receivethe E-DCH allocation within a predetermined channel request responseperiod.
 10. A wireless transmit/receive unit (WTRU) comprising: atransmitter configured to transmit an enhanced dedicated channel (E-DCH)allocation request, wherein the E-DCH allocation is requested includingE-DCH transmission data; and a channel allocation response timerconfigured to time a predetermined channel request response period, andwherein the transmitter is further configured to retransmit an E-DCHallocation request on a condition that an E-DCH allocation is notreceived in response to the E-DCH allocation request within thepredetermined channel request response period and refraining fromfurther requesting the E-DCH retransmitted allocation for a secondpredetermined channel request response period.
 11. A wirelesstransmit/receive unit (WTRU) comprising: a transmitter configured totransmit an enhanced dedicated channel (E-DCH) allocation request; achannel allocation response timer configured to time a predeterminedchannel request response period; and circuitry configured to discarddata for which the E-DCH allocation was requested on a condition thatthe E-DCH allocation is not received in response to the E-DCH allocationrequest within the predetermined channel request response period,wherein the transmitter is further configured to transmit an updatedE-DCH allocation request on a condition that the E-DCH allocation is notreceived in response to the E-DCH allocation request within thepredetermined channel request response period and refraining fromre-requesting the updated E-DCH allocation for a second predeterminedchannel request response period.
 12. A wireless transmit/receive unit(WTRU) comprising: at least one component configured to transmitenhanced uplink (EU) scheduling information on an EU channel; whereinthe at least one component is further configured to start a timer inresponse to the transmitted EU scheduling information; wherein the atleast one component is further configured in response to not receivingan acknowledgment to the transmission of the scheduling information onthe EU channel, to retransmit the scheduling information on the EUchannel; wherein the component is further configured, in response toreceiving an acknowledgement and not receiving an allocation of EUresources, to retransmit the scheduling information or updatedscheduling information on the EU channel after the timer has expired;and the circuitry is configured in response to receiving an allocationof EU resources, to transmit EU data over the EU channel.
 13. The WTRUof claim 12 wherein the acknowledgement is transmitted on a downlink EUsignaling channel.